Just remember, it's all about the bass. Laptop speakers are completely useless. You won't hear a thing! Larger computer speakers with a fat sub-woofer are reasonably good in a smaller room, but it's probably a real nuisance to provide them.
If your lecture hall has a stupendous PA system, that might work. We've seen Thinklabs stethoscopes used in front of live television audiences by a famous TV doctor.
In terms of connection, you can connect the One directly to self-powered loudspeakers like computer speakers, and you can easily connect it into a PA system. We recommend using a loudspeaker with good bass and a long extension cable to avoid acoustic feedback.
Beatspill+ is a recommended loudspeaker choice and has been tested with the stethoscope.